Field of the Invention
The invention relates to an optical apparatus equipped with a rotation restricting mechanism for a plurality of lens holding frames.
Description of the Related Art
As a lens barrel for an optical apparatus, such as a digital camera, there has been known one which is equipped with a zoom mechanism configured to restrict rotation of each of a plurality of lens holders holding a plurality of lenses by a rectilinear motion barrel and move the lens holders along an optical axis by rotation of a cam barrel, to thereby move the lenses to respective predetermined positions.
Recently, in response to an increasing demand for a higher zoom magnification, a lens barrel tends to have a larger number of lenses and have a longer length in its fully extended state, i.e. the lens barrel tends to have a larger size. On the other hand, there is also a demand for reduction of the thickness of an optical apparatus, and hence it is required to minimize the size of the optical apparatus in a retracted state of the lens barrel. To meet this demand, it is envisaged to reduce the thickness of an optical apparatus by connecting barrels, each having a reduced size in the optical axis direction, in a multi-stage configuration, or alternatively by arranging a plurality of cams such that the cams do not cross each other (see e.g. Japanese Patent Laid-Open Publication No. 2001-324663 and Publication of Japanese Patent No. 3842087).
However, in either of the techniques disclosed in Japanese Patent Laid-Open Publication No. 2001-324663 and Publication of Japanese Patent No. 3842087, a rectilinear motion barrel is used to restrict rotation of each of a plurality of lenses, and hence the size of a lens barrel is diametrically increased by an amount corresponding to the thickness of the rectilinear motion barrel. To solve this problem, a lens barrel has been proposed which is configured to advance and retract a plurality of lenses relative to a cam barrel along the optical axis in a state where each of the lenses has its rotation restricted, without providing a rectilinear motion barrel (see e.g. Japanese Patent Laid-Open Publication No. H09-211292).
In this lens barrel disclosed in Japanese Patent Laid-Open Publication No. H09-211292, the cam barrel has an inner peripheral surface formed with cam grooves which correspond to a first group lens, a second group lens, and a third group lens, respectively. In the lens barrel, the third group lens has its rotation restricted by a fixed barrel, the second group lens has its rotation restricted by the third lens, and the first group lens has its rotation restricted by the second lens.
In the lens barrel, however, since the cam grooves corresponding to the respective lenses are all formed in the inner peripheral surface of the single cam barrel, the arrangement of the cam grooves is restricted. Further, the third group lens does not move relative to the cam barrel along the optical axis, but advances and retracts together with the cam barrel along the optical axis, and hence the arrangement of the lenses in the optical axis direction and the motion trajectory of each of the lenses are restricted, which makes it difficult to realize an even higher zoom magnification.